1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a device and method for transporting printed products.
2. Background Information
Web printing presses print a continuous web of material, such as paper. The continuous web then is cut in a cutting unit so as to form book blocks. These book blocks can be sections of a newspaper, for example. In order to transport or process the book blocks, for example to perform a trimming operation, it is often desirable to firmly grip the book using grippers which are moveable along a track.
U.S. Pat. No. 5,727,783 purports to disclose an apparatus for the delivery of sheets of printed products. A plurality of grippers move along a track at a certain pitch and hold the printed products. The printed products however are fixed with relation to their respective gripper, and must be transferred to a deceleration device to be decelerated. This transfer can cause damage to the printed products.
An object of the present invention is to provide for a device and method for gripping and transporting printed products whereby the printed products may move relative to the grippers. An additional or alternative object of the present invention is to reduce potential damage to printed products.
The present invention provides a gripper unit including a housing, and a first gripper arm and a second gripper arm for gripping a printed product, the first and second gripper arms slidingly with respect to the housing. The housing is movable along a track.
Since the first and second gripper arms may slide with respect to the housing, the speed of the printed product held by the gripper arms may be varied with respect to the track velocity. This speed variation may occur even while the printed product is firmly held by the gripper arms.
The first gripper arm preferably is attached to a first bar, and the second gripper arm to a second bar. Each bar is attached at each end to a slidable carriage, slidable in a slot formed in a side of the housing, which preferably is of an inverted U-shape. The first bar preferably is fixed to with respect to the carriages at its end, and the second bar preferably can rotate so as to move the second gripper arm to grasp a printed product against the rotationally-fixed first gripper arm.
The rotatable second bar preferably is spring-loaded with respect to the carriages at its end, so that the second gripper arm is forced into an open position.
An actuating lever attached to the rotatable second bar and one of the carriages can move the second bar against the spring force so that the second gripper arm grasps the printed product. Moreover, a cam can lock over center so as to hold the lever in a closed position. A latch can then lock the lever in the closed position, so that the second bar cannot rotate back to the open position.
Once the latch is unlatched, the product can be released, since the spring-loading of the second bar forces the second gripper arm to an open position.
A cam may also be provided, and connected to a V-shaped hinge having two arms. One arm is connected to the side of the housing and another arm to the slidable carriage. A cam follower acting on the cam can flatten the V-shaped hinge, so as to move the slidable carriage in the slot with respect to the housing. The hinge may lock over center. Each side of the gripper unit preferably has a cam/hinge arrangement.
The present invention also provides a gripping device including a track and a plurality of gripper units running in the track, each gripper unit including a housing, and a first gripper arm and a second gripper arm for gripping a printed product, the first and second gripper arms slidingly supported within the housing.
The gripping device may further include a chain drive for driving the gripper units, preferably at a constant speed. A cam follower may be provided to slide the gripper arms of each gripper unit with respect to the housing, so as to change the velocity of the printed products while the products remain gripped. The cam follower may interact with a cam connected to a slidable carriage supporting the gripper arms within the housing.
The present invention also provides a method of gripping a printed product including gripping a printed product in a gripper unit and moving the printed product with respect to the gripper unit while the printed product remains gripped. The printed products preferably are gripped by two gripper arms and then slid within a slot in a housing during the moving step. Advantageously, a cam interaction can be used to effect the sliding motion.
Preferably, a second of the gripper arms is rotatable and the method includes locking the second arm in a closed position with a latch and releasing the latch to release the product.